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531.
Stephan J. Nix Peter E. Moffa Daniel P. Davis 《Journal of the American Water Resources Association》1991,27(2):189-200
ABSTRACT: A combined sewer system is a complex system subject to the dynamic stimuli of precipitation, runoff pollution loads, and sanitary wastes. The system response is a random series of pollutant loads to a receiving water. In many localities, these discharges create considerable water quality problems. Mathematical models can and have played a useful role in predicting the behavior of combined sewer systems and evaluating abatement strategies. Based on the authors' experiences over the past several years, this paper explores some of the positive and negative aspects of using deterministic mathematical models to simulate the behavior of combined sewer systems. A case study follows a discussion on modeling objectives, limitations of modeling, model selection, establishing model credibility, and many other considerations necessary in modeling and simulating these systems. 相似文献
532.
Hugh Lehman E. Ann Clark Stephan F. Weise 《Journal of Agricultural and Environmental Ethics》1993,6(2):127-143
A number of distinct definitions ofsustainable agriculture have been proposed. In this paper we criticize two such definitions, primarily for conflating sustainability with other objectives such as economic viability and ecological integrity. Finally, we propose and defend a definition which avoids our objections to the other definitions. 相似文献
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535.
Stephan Slingerland Paulien De Jong 《Journal of Environmental Planning and Management》1998,41(2):195-208
An important question in the present reorganization and liberalization of infrastructure networks in many countries is what kind of regulatory regimes can provide incentives for demand management and reduction in a future situation. In this paper, the present situation in the Dutch waste and electricity sectors is analysed. It is concluded that a quantity-based tariff system and the entwined interests of organizations are key impediments to effective demand management in these two sectors. A hypothetical intervention is proposed which aims to remove these two fundamental drawbacks. Some likely consequences of the suggested intervention are discussed. 相似文献
536.
537.
Claudia Borgioli Giovanni Maria Marchetti Felicitas Scapini 《Behavioral ecology and sociobiology》1999,45(2):79-85
Under stressful conditions (e.g. finding themselves on dry or moisture-saturated substrates) littoral talitrids (Crustacea,
Amphipoda) demonstrate zonal orientation, in which they must promptly reach the optimal zone of the beach, the wet fringe
near the shoreline. A relationship might therefore exist between the use of orientation and the frequency of such stressful
conditions in the natural environment. Moreover, the efficiency of orientation toward the sea could be related to the possibility
of using strategies other than zonal orientation in order to avoid stress. This study analysed the actual use and efficiency
of orientation under natural conditions of four Talitrus saltator (Montagu, 1808) populations from Mediterranean and northern European Atlantic coasts with different ecological features.
Orientation tests were carried out on the beach with all natural cues available. Then the same individuals underwent control
experiments to study their sun orientation far from the sea in an experimental arena. The following results emerge from the
comparison of the circular distributions: (1) marked differences among populations in the precision of zonal recovery under
natural conditions; (2) a common solar orientation capacity in the control tests far from the sea; (3) different orientation
choices of the same individuals according to the test conditions, natural or controlled. The habitat diversity of the four
populations (amount, distribution and kind of detritus and wrack on the beach, degree of coastal erosion, orientation of the
shoreline, human use of the beach) provides an ecological interpretation for the differences in orientation observed among
populations.
Received: 13 October 1997 / Accepted after revision: 26 April 1998 相似文献
538.
Federico Cappa Claudia Bruschini Maria Cipollini Giuseppe Pieraccini Rita Cervo 《Die Naturwissenschaften》2014,101(2):149-152
The ability to discriminate among nestmates and non-nestmate is essential to defend social insect colonies from intruders. Over the years, nestmate recognition has been extensively studied in the honeybee Apis mellifera; nevertheless, the quantitative perceptual aspects at the basis of the recognition system represent an unexplored subject in this species. To test the existence of a cuticular hydrocarbons’ quantitative perception threshold for nestmate recognition cues, we conducted behavioural assays by presenting different amounts of a foreign forager’s chemical profile to honeybees at the entrance of their colonies. We found an increase in the explorative and aggressive responses as the amount of cues increased based on a threshold mechanism, highlighting the importance of the quantitative perceptual features for the recognition processes in A. mellifera. 相似文献
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540.
Claudia Dreller Robert E. Page Jr. M. Kim Fondrk 《Behavioral ecology and sociobiology》1999,45(3-4):227-233
Pollen storage in a colony of Apis mellifera is actively regulated by increasing and decreasing pollen foraging according to the “colony's needs.” It has been shown that
nectar foragers indirectly gather information about the nectar supply of the colony from nestmates without estimating the
amount of honey actually stored in the combs. Very little is known about how the actual colony need is perceived with respect
to pollen foraging. Two factors influence the need for pollen: the quantity of pollen stored in cells and the amount of brood.
To elucidate the mechanisms of perception, we changed the environment within normal-sized colonies by adding pollen or young
brood and measured the pollen-foraging activity, while foragers had either direct access to them or not. Our results show
that the amount of stored pollen, young brood, and empty space directly provide important stimuli that affect foraging behavior.
Different mechanisms for forager perception of the change in the environment are discussed.
Received: 13 June 1998 / Accepted after revision: 25 October 1998 相似文献